Abstract
Forced flow heat transfer of hydrogen from a round wire in a vertically-mounted pipe was measured at pressure of 1.5 MPa and temperature of 21 K by applying electrical current to give an exponential heat input (Q=Q0exp(t/τ),τ=10 s) to the round wire. Two round wire heaters, which were made of Pt-Co alloy, with a diameter of 1.2 mm and lengths of 54.5 and 120 mm were set on the central axis of a flow channel made of FRP with inner diameter of 5.7 and 8.0 mm, respectively. Supercritical hydrogen flowed upward in the channel. Flow velocities were varied from 1 to 12.5 m/s. The heat transfer coefficients of supercritical hydrogen were compared with the conventional correlation presented by Shiotsu et al. It was confirmed that the heat transfer coefficients for a round wire were expressed well by the correlation using the hydraulic equivalent diameter.
Highlights
When a superconducting coil wound by cable in conduit conductor (CICC) is cooled by hydrogen under a supercritical pressure, an extraordinary heat at a quench will be cooled down smoothly without a jump to film boiling
Shiotsu et al [3] studied the heat transfer from inner wall of a vertical tube to forced flow of low temperature hydrogen under supercritical pressures for the test tubes with various inner diameters and lengths. Their experimental results were compared with an equation of forced flow heat transfer under supercritical pressures presented beforehand [4] based on experimental data of helium and conventional data for non-cryogenic fluids
The heat transfer curve for each flow velocity consists of a region with a higher gradient and that with a lower gradient
Summary
When a superconducting coil wound by cable in conduit conductor (CICC) is cooled by hydrogen under a supercritical pressure, an extraordinary heat at a quench will be cooled down smoothly without a jump to film boiling. Forced flow heat transfer of low temperature hydrogen under supercritical condition has been studied for a cooling design of rocket engines [1, 2]. These studies were mainly aimed for cooling systems operating near the temperature limitation of metals. Shiotsu et al [3] studied the heat transfer from inner wall of a vertical tube to forced flow of low temperature hydrogen under supercritical pressures for the test tubes with various inner diameters and lengths. It was confirmed that the equation can be applicable to forced flow of hydrogen in heated tubes with wide ranges of diameter and length
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